1. Field of the Invention
This invention relates to an image forming apparatus and a fixing device, and more particularly to an image forming apparatus utilizing an electrophotographic method, such as, e.g., printer, photocopier, facsimile machine, and MFP (Multifunction Peripheral).
2. Description of Related Art
In conventional image forming apparatuses using an electrophotographic method, electrostatic latent images are formed according to image information upon exposing a photosensitive drum surface with an exposure means such as an LED (Light Emitting Diode) head after charging the photosensitive drum surface uniformly with a charge roller, and toner images are formed onto the electrostatic latent images by attaching toner made as a thin layer on a developing roller. Subsequently, the toner images are transferred, with e.g., a transfer roller onto a paper fed from a paper feeding device. The toner images on the paper are then fixed to the paper by a fixing device.
As a conventional image forming apparatus using an electrophotographic method having a fixing device, an apparatus set forth in, e.g., Japanese Patent Application Publication No. 2013-073121(A1) has been known. With the image forming apparatus disclosed in the above publication, the heater applies heat to an endless fixing belt; a nipping portion is formed by pushing a pressure roller placed in opposition to a fixing roller via the fixing belt to sandwich the paper conveyed through the nipping portion, and the toner images are fixed onto the paper by application of heat and pressure.
With such a conventional image forming apparatus having a fixing device using a belt heating method, however, a pad is generally formed for pushing the belt outwardly from the interior at an entrance of the nipping portion. With such a conventional image forming apparatus, when fixing a highly rigid paper such as cardboard, coated paper, label paper, plastic film, the paper may come close on a side of the fixing belt pushed by the pad when the paper is subject to nipping. The toner on the paper in this situation may be melted excessively, thereby possibly causing disadvantages such as gloss blur. In other words, with such a conventional fixing device of the image forming apparatus, good printing quality may not be obtained, depending on the kind of paper, when the paper enters the nipping portion.